feat(sync): Add Kobo/Koreader sync and conflict handling

- Add Kobo markup/sync endpoints for bookshelves
- Add Koreader progress sync with SHA-256 support
- Add sync conflict detection and resolution
- Update ebook scanner for better file matching

internal/handlers/conflicts.go

@@ -64,7 +64,7 @@ type ConflictResolveResponse struct {
 	DevicesSynced    []string        `json:"devices_synced"`
 }
 
-func (h *ConflictHandler) ListConflicts(c echo.Context) error {
+func (h *ConflictHandler) GetConflictsData(c echo.Context) ([]ConflictDetailResponse, int, int, error) {
 	user := c.Get("user").(database.Users)
 
 	status := c.QueryParam("status")
@@ -80,14 +80,11 @@ func (h *ConflictHandler) ListConflicts(c echo.Context) error {
 	})
 
 	if err != nil && err != pgx.ErrNoRows {
-		return echo.NewHTTPError(http.StatusInternalServerError, "failed to list conflicts")
+		return nil, 0, 0, err
 	}
 
-	response := ConflictListResponse{
-		Conflicts:  make([]ConflictDetailResponse, 0),
-		Total:      len(conflicts),
-		Unresolved: 0,
-	}
+	response := make([]ConflictDetailResponse, 0, len(conflicts))
+	unresolvedCount := 0
 
 	for _, conflict := range conflicts {
 		var conflictData map[string]ConflictSourceData
@@ -116,13 +113,26 @@ func (h *ConflictHandler) ListConflicts(c echo.Context) error {
 			}
 		}
 
-		response.Conflicts = append(response.Conflicts, detail)
+		response = append(response, detail)
 		if conflict.ResolutionStatus.String == "unresolved" {
-			response.Unresolved++
+			unresolvedCount++
 		}
 	}
 
-	return c.JSON(http.StatusOK, response)
+	return response, len(response), unresolvedCount, nil
+}
+
+func (h *ConflictHandler) ListConflicts(c echo.Context) error {
+	conflicts, total, unresolved, err := h.GetConflictsData(c)
+	if err != nil {
+		return echo.NewHTTPError(http.StatusInternalServerError, "failed to list conflicts")
+	}
+
+	return c.JSON(http.StatusOK, ConflictListResponse{
+		Conflicts:  conflicts,
+		Total:      total,
+		Unresolved: unresolved,
+	})
 }
 
 func (h *ConflictHandler) GetConflict(c echo.Context) error {